Match lapping valve assemblies

Abstract

A method for match lapping a ball valve assembly including a ball and a seat, the method having the following steps: contacting the seat with the ball; rotating the ball about a first rotational axis; rotating the seat about a second rotational axis; and changing an angle formed at the intersection of the first and second rotational axes. The method may include applying lapping compound to one or both of the seat and ball.

1 . A method for match lapping a ball valve assembly including a ball and a seat, the method comprising: 
 contacting the seat with the ball;    rotating the ball about a first rotational axis;    rotating the seat about a second rotational axis; and    changing an angle formed at the intersection of the first and second rotational axes.    
   
   
       2 . A method for match lapping as claimed in  claim 1 , wherein the contacting the seat with the ball comprises mating the ball with the seat.  
   
   
       3 . A method for match lapping as claimed in  claim 1 , wherein the rotating the ball about a first rotational axis comprises changing the direction of rotation.  
   
   
       4 . A method for match lapping as claimed in  claim 1 , wherein the rotating the ball and the rotating the seat comprise rotating at a rotational speed between about 10 and about 60 revolutions per minute (RPM).  
   
   
       5 . A method for match lapping as claimed in  claim 1 , wherein the rotating the seat about a second rotational axis comprises changing the direction of rotation.  
   
   
       6 . A method for match lapping as claimed in  claim 1 , wherein changing an angle formed at the intersection of the first and second rotational axes comprises increasing the angle and decreasing the angle.  
   
   
       7 . A method for match lapping as claimed in  claim 1 , further comprising rough machining the ball and the seat to within about 0.010 and about 0.020 inches of the desired finished sizes.  
   
   
       8 . A method for match lapping as claimed in  claim 1 , further comprising grinding the ball and the seat to within about 0.001 and about 0.002 inches of the desired finished sizes.  
   
   
       9 . A method for match lapping as claimed in  claim 8 , wherein the grinding is performed to within an RMS of about 8.  
   
   
       10 . A method for match lapping as claimed in  claim 1 , further comprising continuing the rotations of the ball and seat in contact with each other and continuing the changing of the angle between the first and second axes until between about 0.001 and about 0.002 inches of material is removed from one of the ball and the seat.  
   
   
       11 . A method for match lapping as claimed in  claim 1 , further comprising: 
 applying a first lapping compound comprising an abrasive of a first size to one of the seat and the ball;    washing first lapping compound from the seat and the ball;    applying a second lapping compound comprising an abrasive of a second size to one of the seat and the ball, wherein the first size is larger than the second size; and    washing the second lapping compound from the seat and the ball.    
   
   
       12 . A method for match lapping as claimed in  claim 1 , further comprising coating one of the ball and the seat.  
   
   
       13 . A method for match lapping as claimed in  claim 12 , wherein the coating comprises coating with a material comprising one of stellite and tungsten carbide, wherein the coating layer is about 0.005 to about 0.020 inches thick.  
   
   
       14 . A method for match lapping a ball valve assembly including a ball and a seat, the method comprising: 
 rough machining the ball and the seat to within about 0.010 and about 0.020 inches of the desired finished sizes;    grinding the ball and the seat to within about 0.001 and about 0.002 inches of the desired finished sizes;    contacting the seat with the ball;    rotating the ball about a first rotational axis at a rotational speed between about 10 and about 60 revolutions per minute (RPM) and changing the direction of rotation;    rotating the seat about a second rotational axis at a rotational speed between about 10 and about 60 revolutions per minute (RPM) and changing the direction of rotation;    applying a first lapping compound comprising an abrasive of a first size to one of the seat and the ball;    washing first lapping compound from the seat and the ball;    applying a second lapping compound comprising an abrasive of a second size to one of the seat and the ball, wherein the first size is larger than the second size;    washing the second lapping compound from the seat and the ball; and    changing an angle formed at the intersection of the first and second rotational axes by increasing the angle and decreasing the angle.    
   
   
       15 . A ball valve assembly having a ball and a seat manufactured by a method, the method comprising: 
 contacting the seat with the ball;    rotating the ball about a first rotational axis;    rotating the seat about a second rotational axis; and    changing an angle formed at the intersection of the first and second rotational axes.    
   
   
       16 . A ball valve assembly manufactured by the method as claimed in  claim 15 , wherein the rotating the ball about a first rotational axis comprises changing the direction of rotation, wherein the rotating the seat about a second rotational axis comprises changing the direction of rotation, and wherein changing the angle formed at the intersection of the first and second rotational axes comprises increasing the angle and decreasing the angle.  
   
   
       17 . A ball valve assembly manufactured by the method as claimed in  claim 15 , wherein the rotating the ball and the rotating the seat comprise rotating at a rotational speed between about 10 and about 60 revolutions per minute (RPM).  
   
   
       18 . A ball valve assembly manufactured by the method as claimed in  claim 15 , further comprising: 
 rough machining the ball and the seat to within about 0.010 and about 0.020 inches of the desired finished sizes;    grinding the ball and the seat to within about 0.001 and about 0.002 inches of the desired finished sizes, wherein the grinding is performed to within an RMS of about 8; and    continuing the rotations of the ball and seat in contact with each other and continuing the changing of the angle between the first and second axes until between about 0.001 and about 0.002 inches of material is removed from one of the ball and the seat.    
   
   
       19 . A ball valve assembly manufactured by the method as claimed in  claim 15 , further comprising: 
 applying a first lapping compound comprising an abrasive of a first size to one of the seat and the ball;    washing first lapping compound from the seat and the ball;    applying a second lapping compound comprising an abrasive of a second size to one of the seat and the ball, wherein the first size is larger than the second size; and    washing the second lapping compound from the seat and the ball.    
   
   
       20 . A ball valve assembly manufactured by the method as claimed in  claim 15 , further comprising coating one of the ball and the seat with a material comprising one of stellite and tungsten carbide, wherein the coating layer is about 0.005 to about 0.020 inches thick.